When I activate my trainer, it seems like Steam tries to start another instance of the game, since it pops up with a window saying that the app is already running.

How can this be? since I only press F1 to activate trainer and nothing else.But still it wants to run another instance of the game.

I have exactly the same issue. The trainer is activated and as soon as I try to use the trainer, the game crashes, telling me the app is already running.

Lifetime Plus Member to support the crew and devs, because I love the CH trainers! They add so much more value to every game, so please consider upgrading, too: https://www.cheathappens.com/show_board2.asp?headID=127286&titleID=8463